JP2004088332A - Power indication discrimination apparatus and mobile communication terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the accuracy of transmission power control in a mobile communication terminal. <P>SOLUTION: Absolute value calculation sections 91-1, 91-2, 91-3 respectively calculate reception strength values as absolute values of reception amplitudes with respect to signals up to three base station groups. After IIR filters 92-1, 92-2, 92-3, respectively average the reception strength values and a maximum selection section 93 selects a maximum value among the reception strength values. A multiplier 95 multiplies a coefficient stored in a coefficient storage section 94 with the selected maximum reception strength value to obtain a threshold. Hard decision sections 96-1, 96-2, 96-3 use the threshold in common to apply hard decision to transmission power control information transmitted from the base station groups of up to three and an increase / decrease discrimination section 97 discriminates whether power is to be increased or decreased on the basis of the discrimination result. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, in a mobile communication system such as a W-CDMA mobile communication system in which a base station instructs transmission power of a mobile communication terminal, the mobile communication terminal controls transmission power in accordance with the above instruction. About technology.
[0002]
[Prior art]
In a W-CDMA (Wideband Code Division Multiple Access) type mobile communication system, the transmission power of a mobile communication terminal is controlled in order to reduce interference with other communication channels.
[0003]
One of such transmission power control methods is a closed-loop transmission power control method. In the closed-loop transmission power control method specified by 3GPP (3rd Generation Partnership Project), a base station measures a physical quantity corresponding to the communication quality of each mobile communication terminal, and the transmission power should be increased based on the result. It is determined whether the number should be reduced, and the result of the determination is instructed to the mobile communication terminal. This transmission power instruction is performed by the base station transmitting transmission power control information. In the mobile communication terminal, the transmission power is increased or decreased by a fixed amount according to whether the transmission power control information is an Up instruction or a Down instruction.
[0004]
By the way, in a soft handover state in which a link is established simultaneously with a plurality of base stations, the transmission power control information sent from those base stations is not necessarily the same information. That is, the Up instruction and the Down instruction may be simultaneously performed. In such a case, the Down instruction is prioritized, and the mobile communication terminal reduces transmission power. This is because if the transmission power is increased in such a situation, the base station that has issued the Down instruction may cause a decrease in communication quality in another channel.
[0005]
[Problems to be solved by the invention]
Now, the transmission power control information is wirelessly transmitted in two values of “1” and “−1”. For example, “1” is assigned to the Down instruction, and “−1” is assigned to the Up instruction. However, since the transmission power control information is subjected to noise during transmission, when received by the mobile communication terminal, the distribution has a spread as shown in FIG. The horizontal axis in FIG. 5 represents the magnitude of the demodulated signal in the mobile communication terminal, and the vertical axis represents the appearance frequency.
[0006]
The spread of the distribution shown in FIG. 5 increases as the received power decreases. Therefore, when the determination of the instruction content indicated by the transmission power control information is performed by a hard decision with the threshold being “0”, the probability of occurrence of a determination error changes according to the magnitude of the received power.
[0007]
However, when performing a hard decision using a fixed threshold value, there is a risk that the content of an instruction from a base station that reduces received power may be erroneously determined. Also, a determination result having a high probability of occurrence of such a determination error is used with the same weight as a determination result regarding an instruction from another base station, so that there is a possibility that inappropriate transmission power control may be performed.
[0008]
Specifically, in FIG. 6, all three base stations BS1, BS2, and BS3 issue an Up instruction. Therefore, the mobile communication terminal should increase the transmission power. However, since the received power for the base station BS3 is small, the content of the instruction may be erroneously determined to be a Down instruction due to the influence of noise. In this case, the down instruction determined erroneously is given priority, so that the mobile communication terminal must reduce the transmission power. In other words, in a situation where the base station is linked to a base station having poor communication quality, transmission power control in the mobile communication terminal cannot be performed with high accuracy by erroneously determining transmission power information from the base station. .
[0009]
The present invention has been made in view of such circumstances, and an object thereof is to improve the accuracy of transmission power control in a mobile communication terminal.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a measuring unit for measuring a predetermined statistic related to the reception strength of a signal transmitted from a plurality of base station groups, and a statistic measured by the measuring unit is a predetermined statistic. The transmission power control information transmitted from the base station group smaller than the threshold value is considered to indicate an increase in the transmission power, and it is determined whether to increase or decrease the transmission power based on the incoming transmission power control information. Instruction determination means.
[0011]
By taking such a measure, the transmission power is increased or decreased by erroneously determining that the transmission power control information transmitted from the base station group having a low reception strength indicates a decrease in the transmission power. It is prevented that the determination as to whether to perform the operation is affected.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is a block diagram of the mobile communication terminal according to the present embodiment.
[0014]
As shown in FIG. 1, the mobile communication terminal according to this embodiment includes an antenna 1, a duplexer (DUP) 2, an analog demodulator 3, fingers 4-1, 4-2,..., 4-n, a RAKE combiner 5, a selector 6, a digital modulation unit 7, an analog modulation unit 8, a power instruction determination unit 9, and a transmission power control unit 10.
[0015]
A received signal obtained by receiving a signal transmitted from a base station (not shown) by the antenna 1 is input to the analog demodulation unit 3 via the duplexer 2. The received signal undergoes frequency conversion and analog demodulation in the analog demodulation unit 3 and then is converted into digital received data. The received data is input to each of the fingers 4-1, 4-2,..., 4-n.
[0016]
To the fingers 4-1, 4-2,..., 4-n, a spreading code and a path timing relating to different paths are designated by a control unit (not shown). .., 4-n despread the received data using the designated spreading code at a timing corresponding to the designated path timing. .., 4-n extract data arriving from different paths. At this time, if the spreading codes of the base stations belonging to different base station groups are mixedly designated, data transmitted from the plurality of base station groups will be respectively extracted by different fingers. The extracted data is provided to the RAKE combiner 5 and the selector 6, respectively. The base station group indicates a group of base stations transmitting the same transmission power information. In the present embodiment, there is a possibility that spreading codes for up to three base station groups are mixedly specified for the fingers 4-1 to 4-2. That is, this mobile communication terminal may establish a link simultaneously with up to three base station groups.
[0017]
The RAKE combining section 5 includes four combiners 51-1, 51-2, 51-3, and 51-4. All the data directly supplied from the fingers 4-1, 4-2,..., 4-n are supplied to the synthesizer 51-1. The combiner 51-1 RAKE combines these data to obtain received data. The data output from the fingers 4-1, 4-2, 4 -n is appropriately supplied to the synthesizers 51-2, 51-3, 51-4 via the selector 6. The combiners 51-2, 51-3, 51-4 perform RAKE combining of the data supplied from the selector 6. Each of the combiners 51-2, 51-3, and 51-4 supplies the combined data to the power instruction determination unit 9.
[0018]
The selector 6 appropriately supplies the data output from the fingers 4-1, 4-2,..., 4-n to the combiners 51-2, 51-3, 51-4 in response to an instruction from the control unit. .
[0019]
The transmission data is spread spectrum by the digital modulation unit 7. The transmission data subjected to the spread spectrum is subjected to analog modulation, frequency conversion, and amplification by the analog modulation unit 8, and is converted into an analog transmission signal. This transmission signal is supplied to the antenna 1 via the duplexer 2 and transmitted from the antenna 1 by radio. Note that the analog modulator 8 can change the gain at the time of the amplification. The gain is set under the control of the transmission power control unit 10.
[0020]
The power instruction determining unit 9 determines whether to increase or decrease the transmission power based on the data provided from the combiners 51-2, 51-3, 51-4. Then, the power instruction determination unit 9 gives an Up instruction to the transmission power control unit 10 when it determines that the transmission power should be increased, and gives a Down instruction when it determines that it should decrease the transmission power. The transmission power control unit 10 controls the amplification gain in the analog modulation unit 8 so as to increase and decrease the transmission power by a constant value in accordance with the Up instruction and the Down instruction.
[0021]
FIG. 2 is a block diagram of the power instruction determination unit 9. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals.
[0022]
As shown in FIG. 2, the power instruction determination unit 9 includes absolute value calculation units 91-1, 91-2, 91-3, IIR filters 92-1, 92-2, 92-3, a maximum value selection unit 93, a coefficient It includes a storage unit 94, a multiplier 95, hard decision units 96-1, 96-2, 96-3, and an increase / decrease decision unit 97.
[0023]
Data provided from the combiners 51-2, 51-3, 51-4 are sent to absolute value calculation units 91-1, 91-2, 91-3 and hard decision units 96-1, 96-2, 96-3. And given respectively.
[0024]
The absolute value calculators 91-1, 91-2, 91-3 calculate the absolute values of the signal levels indicated by the data provided from the combiners 51-2, 51-3, 51-4, respectively. Absolute value calculation units 91-1, 91-2, 91-3 provide the calculated absolute values to IIR filters 92-1, 92-2, 92-3, respectively.
[0025]
The IIR filters 92-1, 92-2, and 92-3 smooth the absolute values given from the absolute value calculation units 91-1, 91-2, and 91-3, thereby obtaining an average of the absolute values. Get the value. The outputs of the IIR filters 92-1, 92-2, and 92-3 are all supplied to a maximum value selection unit 93.
[0026]
The maximum value selecting section 93 selects the maximum value from three values given from the IIR filters 92-1, 92-2, 92-3. The maximum value selection unit 93 supplies the selected maximum value to the multiplier 95.
[0027]
The coefficient storage unit 94 stores a preset threshold value. Then, the coefficient storage unit 94 gives the stored threshold value to the multiplier 95. Note that the threshold value stored in the coefficient storage unit 94 can be arbitrarily changed and set.
[0028]
The multiplier 95 multiplies the maximum value given from the maximum value selection unit 93 by a coefficient given from the coefficient storage unit 94. The multiplier 95 gives the value obtained by the above multiplication as a common threshold value to the hard decision units 96-1, 96-2, and 96-3.
[0029]
Hard decision sections 96-1, 96-2, and 96-3 give from multiplier 95 whether the data given from combiners 51-2, 51-3, and 51-4 are Up instruction or Down instruction. Hard decision is made using the threshold value obtained. The hard decision sections 96-1, 96-2, and 96-3 all provide the decision results to the increase / decrease decision section 97.
[0030]
The increase / decrease determination unit 97 determines whether to increase or decrease the transmission power according to a predetermined algorithm based on the determination results given from the hard determination units 96-1, 96-2, and 96-3, respectively. Then, the increase / decrease determination unit 97 gives the Up instruction to the transmission power control unit 10 when it determines to increase the transmission power, and gives the Down instruction when it determines to decrease it.
[0031]
Next, the operation of the mobile communication terminal configured as described above will be described. The basic operation related to data transmission / reception is the same as that of a conventional mobile communication terminal, and a description thereof will be omitted. Here, the operation for controlling transmission power in transmission power control section 10 will be described in detail.
[0032]
This mobile communication terminal can simultaneously link with three base station groups as described above. .., 4-n are appropriately assigned up to n of the paths for up to these three base station groups, and data arriving on the paths is extracted. At this time, the selector 6 supplies the data output from the finger to which the path related to the first base station group among the three base station groups is assigned to the combiner 51-2, and the second base station group The data output from the finger to which the path relating to the third base station group is assigned is provided to the combiner 51-3, and the data output from the finger to which the path relating to the third base station group is assigned is provided to the combiner 51-4. Thus, the combiners 51-2, 51-3, and 51-4 perform RAKE combining for each base station group. Then, data of the result of these three RAKE combining operations is supplied to the power instruction determining unit 9.
[0033]
In the power instruction determining unit 9, for each of the three data, the absolute value of the signal level indicated by the data is calculated by the absolute value calculating units 91-1, 91-2, and 91-3. Further, the absolute values output from the absolute value calculation units 91-1, 91-2, 91-3 are smoothed by the IIR filters 92-1, 92-2, 92-3, respectively, thereby removing noise. The received power value is obtained as an average value. That is, the reception intensity value for each of the three base station groups is measured.
[0034]
These three reception intensity values are all given to the maximum value selection section 93, where the maximum reception intensity value is selected. Then, the multiplier 95 multiplies the selected maximum reception intensity value by a coefficient stored in the coefficient storage unit 94. Thereby, the threshold value is obtained by the multiplier 95.
[0035]
In the present embodiment, the transmission power control information is represented by “−1” for the Up instruction and “+1” for the Down instruction. In this case, the coefficient is set within a range that is larger than “0” and smaller than 1. The specific value of the coefficient is appropriately determined in consideration of a communication situation in a mobile communication system that is actually operated, transmission power control conditions determined in the mobile communication system, and the like. Since the coefficient storage unit 94 can arbitrarily change and set the stored threshold value, it is possible to easily cope with a case where an appropriate threshold value changes due to a change in the above condition or the like.
[0036]
Subsequently, a specific example of the determination of the threshold will be described with reference to FIG. Here, a state is shown in which a link is established with two base station groups, BS1 and BS2. It is assumed that the distribution of the amplitude of the received signal in each of the base station groups BS1 and BS2 is in the state shown in FIG. In FIG. 3, the horizontal axis represents the signal amplitude of the demodulated transmission power control information, and the vertical axis represents the appearance frequency of the signal amplitude.
[0037]
In the state shown in FIG. 3, the average value of the reception amplitude is L1 for the base station group BS1 and L2 for the base station group BS2. In the absolute value calculation units 91-1, 91-2, 91-3 and the IIR filters 92-1, 92-2, 92-3, the values corresponding to the absolute values of the reception amplitude values L1, L2 are received by the above-described operation. It will be calculated as an intensity value. In FIG. 3, the level indicated by L11 is the reception intensity value for the base station group BS1, and the level indicated by L12 is the reception intensity value for the base station group BS2. Then, the larger one of the reception intensity values L11 and L12 is selected by the maximum value selection unit 93, and is supplied to the multiplier 95.
[0038]
The received intensity value L12 is multiplied by a coefficient in a multiplier 95, and as a result, a threshold value is obtained. As described above, the coefficient is set within a range that is larger than “0” and smaller than 1, so that the threshold is larger than “0” and smaller than the reception intensity value L12. It is obtained as a value as shown in FIG.
[0039]
As described above, the threshold is set to a value larger than “0” corresponding to the maximum reception intensity value within a range not exceeding the maximum reception intensity value. The threshold values set in this manner are used by hard decision sections 96-1, 96-2, and 96-3 for hard decision of the transmission power control signal for the base station group for which the maximum reception intensity value is obtained. It is also commonly used for transmission power control signals for other base station groups.
[0040]
The hard decision sections 96-1, 96-2, and 96-3 determine that the amplitude of the transmission power control information is less than the threshold value, and determine that the amplitude is equal to or greater than the threshold value, and determine that the amplitude is lower than the threshold value. Accordingly, since the threshold is set to a value larger than “0” as described above, the range for determining the Up instruction is set to be larger than the range for determining the Down instruction. As a result, there is a high probability that the transmission power control information transmitted from the base station group whose reception amplitude is small is determined to be an Up instruction. Further, the threshold value is set to a larger value as the maximum reception intensity value is larger. For this reason, the probability that the transmission power control information transmitted from the base station group whose reception amplitude is small is determined to be the Up instruction increases as the maximum reception intensity value increases.
[0041]
That is, in the hard decision units 96-1, 96-2, and 96-3, the transmission power control information from the base station group having a relatively low reception intensity value indicates the Up instruction even if it has the same polarity amplitude as the Down instruction. Will be considered.
[0042]
The increase / decrease determiner 97 determines the increase / decrease of the transmission power by an algorithm as shown in FIG. 4 based on the determination results of the hard determiners 96-1, 96-2 and 96-3. FIG. 4A shows an algorithm when a link is established with two base station groups, and FIG. 4B shows an algorithm when a link is established with three base station groups.
[0043]
As can be seen from FIG. 4, the increase / decrease determination unit 97 determines to increase the transmission power only when it is determined that the transmission power control information is the Up instruction for all of the base station groups that have established links. The increase / decrease determination unit 97 determines a decrease in transmission power when it is determined that the transmission power control information is a Down instruction even for one of the base stations with which a link is established.
[0044]
For this reason, even if the transmission power control information transmitted from the base station group whose reception amplitude is small as described above is regarded as the Up instruction, even if the transmission power control information transmitted from the other base station groups has a larger reception amplitude, The increase or decrease of the transmission power is determined depending on the result of the determination regarding the transmission power control information. That is, in the present embodiment, this is equivalent to ignoring the transmission power control information transmitted from the base station group having the reduced reception amplitude.
[0045]
Thus, according to the present embodiment, regardless of the transmission power control information that is a reception intensity value that is somewhat smaller than the maximum reception intensity value, mainly using transmission power control information with a large reception intensity value, that is, good reception quality is used. The transmission power is increased or decreased. For this reason, it is possible to eliminate the adverse effect of the transmission power control information of poor reception quality and realize accurate transmission power control. In addition, since the threshold value is dynamically determined according to the maximum reception intensity value, it is possible to appropriately select transmission power control information in consideration of the transmission path conditions that change from moment to moment, and achieve high accuracy. Transmission power control can be performed.
[0046]
Further, according to the present embodiment, the reception intensity value used for determining the threshold value is an average value obtained by the IIR filters 92-1, 92-2, and 92-3. The threshold value can be determined stably without being affected.
[0047]
Further, according to the present embodiment, since the IIR filters 92-1, 92-2, and 92-3 are used, the circuit scale can be reduced as compared with the case where a FIR (Finite Impulse Response) filter or the like is used. It is.
[0048]
Further, according to the present embodiment, the range of the reception amplitude of the transmission power control information regarded as the Up instruction is changed by changing the threshold, so that the transmission power control information is either the Up instruction or the Down instruction. It is possible to perform a high-speed determination by a hard determination as in the related art.
[0049]
The present invention is not limited to the above embodiment. For example, the reception intensity value used for determining the threshold value can be applied as long as the reception intensity value is relatively large based on other reception intensity values, for example, a reception intensity value slightly smaller than the maximum reception intensity value. is there.
[0050]
If the polarity of the signal amplitude of the Down instruction is positive, it can be dealt with by setting the coefficient to a negative value. Alternatively, it is also possible to convert all the values calculated by the absolute value calculation units 91-1, 91-2, and 91-3 into negative values and select a relatively small value from those values.
[0051]
Further, the instruction from the base station group having a relatively small received power value may be unconditionally determined as the Up instruction without changing the threshold value.
[0052]
Further, the range of numerical values that can be a coefficient changes according to various conditions in the mobile communication system and the like, and should be appropriately set in consideration of such conditions.
[0053]
Further, the calculation of the average value of the reception intensity value can be performed using another type of filter such as an FIR filter or by another method such as software calculation. good.
[0054]
In addition, although the average value of the reception intensity value indicating the magnitude of the reception amplitude is used as the statistic related to the reception intensity, a value such as the median value or the mode of the distribution of the reception intensity value is applied. It is also possible.
[0055]
Also, the present invention is applicable to a mobile communication terminal configured to link simultaneously with only two base station groups or four or more base station groups.
[0056]
In addition, various modifications can be made without departing from the spirit of the present invention.
[0057]
【The invention's effect】
According to the present invention, a predetermined statistic related to the reception strength of a signal transmitted from a plurality of base station groups is measured, and a transmission statistic transmitted from a base station group whose measured statistic is smaller than a predetermined threshold value is measured. The power control information is assumed to indicate an increase in the transmission power while determining whether to increase or decrease the transmission power based on the incoming transmission power control information. The transmission power control information transmitted from the erroneous determination that the transmission power control information is instructed to reduce the transmission power is prevented from being affected by the determination of whether to increase or decrease the transmission power. As a result, It is possible to improve the accuracy of transmission power control.
[Brief description of the drawings]
FIG. 1 is a block diagram of a mobile communication terminal according to an embodiment of the present invention.
FIG. 2 is a block diagram of a power instruction determining unit in FIG. 1;
FIG. 3 is a diagram illustrating a specific example of determining a threshold.
FIG. 4 is an algorithm for determining an increase or decrease in transmission power.
FIG. 5 is a diagram showing a distribution of a demodulated signal magnitude and its appearance frequency in a mobile communication terminal with respect to transmission power control information.
FIG. 6 is a diagram illustrating an example of a situation in which an erroneous determination occurs in determination of an increase or decrease in transmission power.
[Explanation of symbols]
1: Antenna 2: Duplexer (DUP)
3. Analog demodulators 4-1 4-2, 4-n Finger 5 RAKE combiner 6 Selector 7 Digital modulator 8 Analog modulator 9 Power instruction determiner 10 Transmit power controller 51 -1, 51-2, 51-3, 51-4... Synthesizers 91-1, 91-2, 91-3... Absolute value calculation units 92-1, 92-2, 92-3... IIR filter 93. Value selection unit 94 Coefficient storage unit 95 Multipliers 96-1, 96-2, 96-3 Hard decision unit 97 Increase / decrease decision unit

Claims (10)

For each base station group to which at least one base station belongs, increase / decrease of the individual transmission power of the mobile communication terminal is determined, and transmission power control information indicating the increase / decrease in signal levels of different polarities is transmitted from the base station to each mobile communication terminal. In a power instruction determination device applied to a mobile communication terminal used in a mobile communication system transmitting toward,
Measuring means for measuring a predetermined statistic regarding the reception strength of a signal transmitted from a plurality of base station groups,
The transmission power control information transmitted from the base station group in which the statistic measured by the measuring means is smaller than a predetermined threshold is determined based on the transmission power control information arriving while assuming that the transmission power control information indicates an increase in the transmission power. Instruction determining means for determining whether to increase or decrease the power instruction. The power instruction determination device according to claim 2, wherein the measurement unit measures an average value of reception strength values of signals transmitted from a plurality of base station groups as the statistic. The power instruction determination device according to claim 2, wherein the measurement unit obtains the average value using an IIR (Infinite Impulse Response) filter. The instruction determining means,
Selecting means for selecting one relatively large statistic from among the statistics measured by the measuring means;
Determining means for determining a threshold based on the statistic selected by the selecting means;
Using the threshold determined by the determination means, hard decision means for hard-determining the transmission power control information transmitted from the plurality of base station groups,
The power instruction determination device according to claim 1, further comprising: an increase / decrease determination unit configured to determine whether to increase or decrease transmission power based on a result of the hard determination by the hard determination unit. The method according to claim 4, wherein the determining means determines the threshold value between a number representing the statistic selected by the selecting means and a numerical value consisting of a polarity assigned to transmission power control information indicating a decrease in transmission power and zero. The power instruction determination device according to claim 1. The power instruction determination device according to claim 4, wherein the selection unit selects a maximum statistic from among the statistic measured by the measurement unit. The power instruction determination device according to claim 4, wherein the determination unit sets a value obtained by multiplying a statistic selected by the selection unit by a predetermined coefficient as the threshold. 8. The coefficient according to claim 7, wherein the determining unit uses a numerical value including a predetermined number greater than 0 and less than 1 and a polarity assigned to transmission power control information indicating a decrease in transmission power as the coefficient. 9. Power instruction determination device. The power instruction determination device according to claim 7, wherein the determination unit is capable of changing the coefficient. Mobile communication for determining increase / decrease of individual transmission power of a mobile communication terminal for each base station group to which at least one base station belongs, and transmitting transmission power control information indicating the increase / decrease from the base station to each mobile communication terminal In the mobile communication terminal used in the system,
Transmitting means capable of performing wireless transmission toward the base station while changing its transmission power,
Measuring means for measuring a predetermined statistic regarding the reception strength of a signal transmitted from a plurality of base station groups,
The transmission power control information transmitted from the base station group in which the statistic measured by the measuring means is smaller than a predetermined threshold is determined based on the transmission power control information arriving while assuming that the transmission power control information indicates an increase in the transmission power. Instruction determination means for determining whether to increase or decrease,
A mobile communication terminal comprising: a control unit that controls the transmission unit so as to increase or decrease the transmission power according to a result of the determination by the instruction determination unit.

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